Duplicating mechanism



June 15, 1943. T, F. )BRACKET-r l 2,321,984

DUPLICATING MEGHANISM Filed Feb. 1s, 1941 4 Sheets-Sheet 1- nventor uw m 5 k C m Bn, W f WM.

June 15, 1943- T. F. BRACKETT 2,321,984

' DUPLICATING -MECHANISM *I Filed Feb.,15,'1941 4 sheets-sheet 2 June 15, 1943.

' DUPLICATING MECHANISM 4 Sheets-Sheet 3 T.y F'. B RACK'ETT 2,321,984

' Fil-ed Feb. 15, 1941 nventor (Ittornegs June 15, 1943. T. F. BRAcKE'rT 2,321,984

n UPLCATNG MECHANISM v Filed Feb. 1,3, 1941 4 sheets-sheet 4 Snventor Y Bn l l i Gttomeg Patented June 15, 1943 UNITED STATES PATENT oFElcEf may F. Bracken, nea-oit, man., asignaup General Motors Corporation, Detroit, Mich., a corporation of Delaware Application February 13, '1941, Serial No. 378,746

s claims. (ci. :ao-13.5)

The invention relates to mechanism for reproducing a surface and is animprovement over the co-pending application Serial No. 156,644, led July 31, 1937 in my name, entitled Photo-cell control for die-sinking machine" which has become Patent Number 2,242,506. That application discloses means whereby any contour or shape may be reproduced from a model by driving a tracer head over the surface ofthe model and controlling cutting mechanism by the variations in the travel of the tracer. It has been customary in devices of this kind to use a router or round end end-mill to cut the surface of the blank to reproduce theoriginal model and this leaves a series of curved grooves on the surface of the generated model as the cutter is fed across said surface. It is therefore necessary after the generated model has been roughly completed by this means to perform another operation thereon to smooth down the surface, such as sanding, etc.

If, however, a different type of cutting mechanism is used, such as a cylindrical rotating cutter similar to that used on planers and joiners, then the angularity of the cutter must vhe altered as well as its longitudinal position before a satisfactory model can be generated. The use of a cylindricalV cutter will eliminate ridges and provide a substantially smooth generated surface.

It is therefore an object of my present invention to provide means using a rotating cutter whose tangency to a desired generated surface will be maintained and its position varied, depending upon the curvature of the original model, so that the same will be tangent at all times to the desired generated surface and thus avoid the above mentioned ridges and grooves and provide a substantially smooth generatedY surface. Y

It is a further object 'of my invention to provide rotating cutting means which will be maintained rial No. 156,644, showing my invention applied thereto;

'Figure 2. is a top plan view of the same mal chine;

Figure 3v is an enlarged detailed view showing the follower or tracer mechanism which rides along the surface of the original model;

Figure 4 is a sectional view taken on line 4-4 of Figure 3;

Figure 5 is a sectional view taken on a portion of line 5 5 of Figure 3; l'

Figure is an enlarged detailed vertical view showing the cutting means controlled by the tracer; and

Figure 'I is a view taken at right angles to Figure 6 showing the same cutting mechanism.

Referring now more speciiicallytc the drawings, there is shown in Figure 1 a stationary box frame 2 within which is mounted for longi- Y tudinal movement with respect thereto a smaller sub-frame 4 which is driven by suitable apparatus housed within.the enclosure 6 and driving a rotatable shaft 8 engaging a portion of said frame. There is mounted upon suitable stationary structure I0 a master model l2 and also at the opposite end of the stationary frame a' supporting member i4 which has mounted thereon a blank i6 in which may be cut the surface it is desired to reproduce. A tracing mechanism, generally indicated at I8, is mounted on a vertical support 2l carired by the movable frame, said vertical rod being capable of transverse movement across the movable Vframe and being driven by mechanism housed within the enclosure 22 driving through shafts 24 and 26. follower mechanism may also be driven vertically on the shaft 2l! by a threaded rod 28 driven by mechanism housed within the enclosure 30. It is thus possible to drive the tracer mechanism in any one of three directions by the means S, 22- and 30 respectively.

Whichever driving means is being used for the scanning direction simultaneously drives a 38 which is driven synchronously with the -h threaded rod 2i driving the tracer. Since this column 32 is also carried by the movable Yframe, it is obvious that. it will be moved ,longitudinally `at the same time that column 2l is so moved.

The operation of such a type of device as described in S. N. 156,644 is that the tracer, and, of

course, the cutter, are placed in one extremity of the model to be reproduced and the blank, re-

spectively, and then let us say that the driving means 22 is energized to cause the tracer member machine, the tracer, being in cotact with the master model as 'it is driven transversely, in folT lowing the model contour moves in and out or longitudinally of the whole structure. This movement in and out controls the longitudinal driving meansli to move the whole movable carriage, thus moving the cutter to follow a similar contour in lthe blank and at the same time correct to bring the tracer back to a position where it will no longer call for movement. However, in scanning the master surface and in cutting the blank with a round end end-mill, as the cutter moves back and forth across the model ridges will be left in the blank as the surface is generated by the end-mill. I therefore use a cylindrical rotating cutter to cut the surface to overcome this disadvantage.

Referring now more specifically to Figures 6 and 7, there is shown therein mounted upon the vertical column 32 a slidable sleeve 40 to which is integrally secured a horizontal tube 62 which extends on both sides of the column 32, one end carrying internally threaded means 64 which engages the threaded rod 36 to cause the device to be driven vertically, if desired, and the opposite end carrying a sleeve 46 which has a plurality of ears or lugs extending therefrom to support desired apparatus. One angled member 48 has secured thereto by suitable bolts 50 a small control motor 52. Extending upwardly from said sleeve 46 is an arm 56 which pivotally supports a long crank arm 55 at a proximate center point, said arm supporting in turn a second driving motor 56 which rotates the cutter member 58 per se.

A third projecting flange 68 supports on its outer end a bushing 62 within which is mounted one section of a rotatable cylindrical member 64 which is made integrally with a worm wheel 66.

. Through the center of the compound member 64-66 is drilled an opening 68 which is internally threaded and through which Yis screwed one end of an eye bolt 10. The threaded portion of the worm wheel 66 engages with a worm l2 mounted on the shaft 14 of the motor 52 and is adapted to be driven thereby. The outer surface of the member 64 which projects through the bushing 62 is externally threaded asshown at 76 and a large nut 'I8 is applied thereto to hold the member within the bushing but is not tightened to an extent which will prevent 64 from turning, but only to keep it snug.

Projecting from one side of the motor housing of the motor 56 is a pin 80 which projects into the eye 82 of the eye bolt 'l0 and thus causes the motor 56 to pivot around its support as the eye bolt is forced up or down as shown in Figure 6. The end 86 of the arm has secured thereto one end of a Bowden wire 88 by a suitable set screw 80. The exterior cable 92 of the Bowden wire is supported by a bracket 94 from the motor housing 52. This Bowden wire assembly continues over to the tracing mechanism. It is thus eviand the cutter to move transversely across the that only a sufficient amount of correction will be applied at one time.

The tracer mechanism on the other hand is best shown in Figure 3 and there again we have the vertical column around which a slidable sleeve 98 is applied and which again carries a horizontal rod 98one end of which supports an internally threaded member |00 which is associated with the vertical driving threaded means 28 to move the assembly up and down on the column 20. A supporting member |02 is applied to the opposite end of the transverse rod 98 and ls secured thereto by a suitable set screw |04, the upper portion of the member |02 being drilled out to form a cavity |06 within which is pivoted a bell crank |08 engaging a motion transfer rod dent that when the motor 52 is energized the worm 'I2 driven thereby will cause the worm `wheel 66 to rotate and thus cause the threaded I0 on the control mechanism. There is also provided a longitudinal bushing ||2 which supports the shaft ||4 of a plunger member which transmits follower motion to the control.

The lower portion of the supporting member |02 is in the nature ofa plate surface t8 which carries thereon certain switching means pivoted about the axis of a bolt |20., This switching means comprises an elongated flat lever |22 which is pivoted about said bolt as best shown in Figure 5, and is biased toward its uppermost position by a suitable leaf spring |24 which is anchored on the plate ||8. Mounted on this plate l22 are two spaced contact switch members 26 and |28 and secured to one corner is the opposite end of the Bowden wire 88, the exterior stationary portion 92 of which is secured to the plate I I8. Also pivotally mounted on the bolt |20 around a sleeve |30 is a bell crank member |32, one end of which supports a cylindrical tracer |34, said follower |34 having a shaft |36 which projects.

down into an opening in theupper end of the bell crank lever and ismounted upon a pair of ball bearing assemblies |38 for easy rotation. The end of the plunger ||4 is adapted to ride against the side of the bell crank lever |32 to hold the tracer |34 under some slight pressure against the side of the master model and transmit its motion to the control means.

The opposite end of the bell crank lever contains a switch point |40 which oscillates between the two switch points |26 and |28 carried on the pivotal plate |22. It will thus be evident that as the tracer |34 is driven, let us say transversely across the surface o'f the master model, the contour thereof `will force it back and cause the bell crank |32 to rotate about the pivot vpoint of the tact with switch point |26; this will energize the motor 52 and cause the same to rotate in such a direction that the threaded portion 10 of the eye bolt will be drawn down to rotate motor housing 56 counterclockwise about its pivot, as shown in Figure 6, and pull the rotating cutter 58 slightly away from the blank and thus cause the same correction that the tracer has called for.y The motor'52 'is rotatable in either direction, depending upon which circuit is made. However,'when the motor housing 56 makes this particular motion it pulls the Bowden wire 88 outwardly from the sleeve 92, which motion is translated to the tracer in which the -wire 88 is pulled downward to move the plate |22 counterclockwise around the pivot |20. This tends to move contact |26 away from contact 40 and when the plate |22 has moved far enough to break the contact the motor 52 will be deenergized and the 'cutter will tudinal travel of the movable frame to make whatever longitudinal correction of lthe tracer and cutter is necessary. v

- It should also be pointed out that the tracer roller and the cutter are the same size and character, are located on their mountings at the same distance from the pivot point and are initially positioned in the same upright position vso that the surfaces traced and generated will be as near identical'as possible. l

I claim: v l. In a device of the class described, a model having a curved surface that it is'desi'red to reproduce, a cylindrical roller tracer pivotally mounted to engage said surface, a cylindrical rotary cutter independently pivotally mounted to engage a blank to be cut means to simultaneously move both the tracer and cutter across the model.

and blank respectively and means interconnecting said tracer and cutter to cause one to move if the other is forced about its pivot. v

2. In a device for reproducing surfaces, a cylindrical tracer head, means for mounting said head to roll over a surface, lpivotal means for said mounting, means for driving said tracer head across said surface, whereby as it travels thereover it will move pivotally, a cylindrical cutter independently similarly pivotally mounted to cut a generated surface on a blank, means simultaneously moving said cutter with said tracer and means interconnecting saidtracer and said cutter whereby any pivotal movement of the tracer as it is moved will cause the cutter to duplicate such pivotal movement to maintain the same in a tangential position with respect to the surface being developed.

3..In a surface reproducing device having a model and a blank mounted in spaced relation, a cylindrical tracer head pivotally mounted adjacent the model tangent to the surface thereof, a cylindrical cutter independently pivotally mounted adjacent the fblank substantially tangent thereto, means for simultaneously moving the tracer and cutter across the model and blank respectively and means interconnecting the tracer head and cutter to cause one to move about its pivot if the other rotates about its own and thus remain substantially parallel.

4. In a surface reproducing device having a model and a blank mounted in spaced relation, a

carriage movable in a plane normal to' the surfaces of the model and blank, .a rotatable cylindrical tracer head pivotally mounted on the carriage adjacent the model so that its cylindrical surfacel rolls on the modelsurface and is substantially tangential thereto, a rotatable cylindrical cutter pivotally mounted on the carriage adjacent the blank in substantial tangential contact therewith, and means interconnecting the pivoted tracer head and cutter to transmit any rotation of the tracer head about its pivot to the cutter head so that the'two will remain in substantial parallelism at all times.

5. In a surface reproducing device having a model and a blank mounted in spaced relation, a carriage movable in a plane normal to the surfaces of the model and blank, a rotatable cylindrical tracer head pivotally mounted on the carriage adjacent the model so that its cylindrical surface rolls on the model surface and is substantially tangential thereto, a rotatable cylindrical cutter pivotally mountedon thecarriage adjacent the blankin substantial tangential contact therewith, means to move said cutter about its pivot and means operated by the position of the vtracer head to control the last-named Inov. ing means.

6. In a surface reproducing device having a model and a blank mounted in spaced relation,

a carriage movable in a plane normal to the sur- Y cent the blank in substantial tangential contact therewith, electrical means to move said cutter about its pivot and switching means actuated by the tracer head to control the electrical means.

TRACY F. BRACKET?. 

